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Articles

Modification of Cytokinins by Cauliflower Microsomal Enzymes ¹

Department of Life Science and Biomedical Research Institute, University of Wisconsin-Parkside, Kenosha, Wisconsin 53141

N⁶-(²-isopentenyl)Adenine and N⁶-(²-isopentenyl)adenosine were hydroxylated, respectively, to 6-(4-hydroxy-3-methyl-trans-2-butenylamino)purine and 6-(4-hydroxy-3-methyl-trans-2-butenylamino) -9--ribofuranosylpurine in the presence of NADPH and the microsomal fraction from cauliflowers (Brassica oleracea L.). The hydroxylating reaction was completely inhibited by 10 millimolars metyrapone and partially inactivated by 10-minute treatment of the microsomal preparation with ethylene. The cytokinins were also dealkylated by the microsomal enzymes and formed adenine from cytokinin base and adenosine from cytokinin nucleoside. These results suggest that plant cytochrome P-450 is involved in the conversion of one type of cytokinin to another, and in the modification of cytokinin molecules.

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